Abstract

Several growth hypotheses have been tested to investigate why males of the sequential hermaphrodite, Mediterranean rainbow wrasse, Coris julis (Linnaeus, 1758), are relatively larger than females of the same age. Individual growth trajectories were estimated to test these hypotheses. A good linear relationship between otolith size and body size was observed (r2 = 0.71, n = 609), thus, past somatic growth of any specific fish can be inferred from the longitudinal data described by the width of annual increments in the otolith. These data were successfully analyzed by a non-linear mixed-effect model (von Bertalanffy growth model) using a Bayesian approach. The results obtained suggest that Mediterranean rainbow wrasse secondary males are relatively larger than females because 1) fish that change sex are already the larger individuals in their age group (specifically those with higher growth rate, ksecondary males = 0.199 and kfemales = 0.161) and 2) they experience a growth spurt after sex change. The differences in growth observed in this species and in other protogynous hermaphrodites could be related to differences in social organization, which, in turn, are related to differences in the sex change mechanisms.

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Acknowledgements

We thank to N. Jaume, E. Ceballos and I. Álvarez for their assistance during otolith extraction. This work has been financed by the Spanish Ministry of Education and Science (project ROQUER CTM2005-00283). M. Linde was partially supported by “Direcció General de Recerca, Desenvolupament Tecnològic i Innovació” (“Conselleria d’Economia, Hisenda i Innovació”). J. Alós was supported by a FPI fellowship (MICINN).